U.S. patent application number 11/109567 was filed with the patent office on 2005-10-20 for dual length block codes for multi-band ofdm.
This patent application is currently assigned to Texas Instruments Incorporated. Invention is credited to Balakrishnan, Jaiganesh, Batra, Anuj.
Application Number | 20050232139 11/109567 |
Document ID | / |
Family ID | 35096160 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050232139 |
Kind Code |
A1 |
Balakrishnan, Jaiganesh ; et
al. |
October 20, 2005 |
Dual length block codes for multi-band OFDM
Abstract
A transmitter 200 is provided. The transmitter 200 comprises a
block encoder 203 operable to encode a bit stream using a first
block size for a first portion of a message according to an
orthogonal frequency division multiplex protocol and a second block
size for a second portion of the message.
Inventors: |
Balakrishnan, Jaiganesh;
(Bangalore, IN) ; Batra, Anuj; (Dallas,
TX) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
|
Assignee: |
Texas Instruments
Incorporated
Dallas
TX
|
Family ID: |
35096160 |
Appl. No.: |
11/109567 |
Filed: |
April 19, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60564032 |
Apr 20, 2004 |
|
|
|
Current U.S.
Class: |
370/208 ;
370/465 |
Current CPC
Class: |
H04L 1/0071 20130101;
H04L 1/0057 20130101; H04L 27/2602 20130101; H04J 13/16
20130101 |
Class at
Publication: |
370/208 ;
370/465 |
International
Class: |
H04J 003/22; H04J
003/16; H04J 003/00; H04J 011/00 |
Claims
What is claimed is:
1. A transmitter, comprised of: a block encoder operable to encode
a bit stream using a first block size for a first portion of a
message according to an orthogonal frequency division multiplex
protocol and a second block size for a second portion of the
message.
2. The transmitter of claim 1, wherein the transmitter further
includes: a scrambler component operable to scramble the bit stream
received from a higher layer application and to provide the
scrambled bit stream to the block encoder; an interleaver component
operable to interleave blocks of bits received from the block
encoder; a mapper operable to mount the output of the interleaver
onto quadrature amplitude modulation constellations; an inverse
fast Fourier transformer component operable to transform the output
of the mapper to the time domain; and a digital-to-analog converter
operable to convert the output of the inverse fast Fourier
transformer component to an analog signal.
3. The transmitter of claim 3, wherein the number of bits contained
by the first block size is a rational multiple of the number of
bits contained by the second block size.
4. The transmitter of claim 3, wherein the first block size is
greater than the second block size, and a length of the second
portion of the message is less than or equal to the first block
size.
5. The transmitter of claim 2, wherein the second block size is
sized to encode six orthogonal frequency division multiplex
symbols.
6. The transmitter of claim 1, wherein the length of the first
block size and of the second block size are a pair selected from
the group of pairs consisting of (2400 bits, 1200 bits), (2400
bits, 600 bits), (2400 bits, 300 bits), (1200 bits, 600 bits),
(1200 bits, 300 bits), and (600 bits, 300 bits).
7. A method of communicating, comprising: block encoding a first
portion of a message according to a multi-band orthogonal frequency
division multiplex protocol into a plurality of blocks having a
first length; and block encoding a second portion of the message
into one or more blocks having a second length, the second length
being less than the first length.
8. The method of claim 7, further including: block encoding a third
portion of the message into one or more blocks having a third
length, the third length being less than the second length.
9. The method of claim 7, further including: block decoding the
first portion of the message based on the first length; determining
the end of the first portion of the message based on a message
length contained in a header in the first portion of the message;
and block decoding the second portion of the message based on the
second length.
10. The method of claim 7, wherein the number of bits of the first
length is a rational multiple of the number of bits of the second
length.
11. The method of claim 7, wherein the second length conforms to
the length of six orthogonal frequency division multiplex
symbols.
12. The method of claim 7, wherein the second length is in the
range of about the length of one orthogonal frequency division
multiplex symbol to the length of the number of orthogonal
frequency division multiplex symbols that conforms to the period of
the time-frequency codes of an orthogonal frequency division
multiplex communication standard employed in the communication.
13. The method of claim 7, wherein the second length is selected to
promote communications at or below a specified packet error
rate.
14. The method of claim 7, wherein the second length is selected to
reduce a decoding latency associated with the first length.
15. A communication system, including: a first transceiver
operable, using a first block size to block encode a first portion
of a message according to a multi-band orthogonal frequency
division multiplex protocol and using a second block size to block
encode a second portion of the message, the first transceiver
further operable to transmit the message; and a second transceiver
operable to receive the message using a block decoder to decode the
first portion of the message based on the first block size and to
decode the second portion of the message based on the second block
size, wherein the second transceiver distinguishes the first
portion of the message from the second portion of the message based
on a message length indication provided in the first portion of the
message.
16. The system of claim 15, wherein the first transceiver and the
second transceiver communicate in accordance with a protocol
selected from the group consisting of a Multi-band Orthogonal
Frequency Division Multiplex Special Interest Group Physical Layer
specification, a WiMedia wireless personal area network protocol,
and a Ecma wireless personal area network protocol.
17. The system of claim 15, wherein one of the transceivers is a
piconet controller.
18. The system of claim 15, wherein the second block size is
selected to reduce decoding latency at the second transceiver while
continuing to satisfy a maximum packet error rate
specification.
19. The system of claim 15, wherein the first and second
transceiver negotiate the first block size and the second block
size during an initialization session.
20. The system of claim 15, wherein the number of bits of the first
block size is a rational multiple of the number of bits of the
second block size.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 60/564,032 filed Apr. 20, 2004, and entitled "Dual
Length Block Codes for Multi-band OFDM" by inventors Jaiganesh
Balakrishnan, et al, which is incorporated herein by reference for
all purposes.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] The present disclosure is directed to communications, and
more particularly, but not by way of limitation, to a system and
method for communicating employing dual length block codes for
multi-band orthogonal frequency division multiplex (OFDM).
BACKGROUND OF THE INVENTION
[0005] A network provides for communication among members of the
network. Wireless networks allow connectionless communications.
Wireless local area networks are generally tailored for use by
computers and may employ sophisticated protocols to promote
communications. Wireless personal area networks with ranges of
about 10 meters are poised for growth, and increasing engineering
development effort is committed to developing protocols supporting
wireless personal area networks.
[0006] With limited range, wireless personal area networks may have
fewer members and require less power than wireless local area
networks. The IEEE (Institute of Electrical and Electronics
Engineers) is developing the IEEE 802.15.3a wireless personal area
network standard. The term piconet refers to a wireless personal
area network having an ad hoc topology comprising communicating
devices. The piconet may be coordinated by a piconet coordinator
(PNC). Piconets may form, reform, and abate spontaneously as
various wireless devices enter and leave each other's proximity.
Piconets may be characterized by their limited temporal and spatial
extent. Physically adjacent wireless devices may group themselves
into multiple piconets running simultaneously.
[0007] One proposal to the IEEE 802.15.3a task group divides the
7.5 GHz ultra wide band (UWB) bandwidth from 3.1 GHz to 10.6 GHz
into fourteen bands, where each band is 528 MHz wide. These
fourteen bands are organized into four band groups each having
three 528 MHz bands and one band group of two 528 MHz bands. An
example piconet may transmit a first multi-band orthogonal
frequency division multiplex (MB-OFDM) symbol in a first 312.5 nS
duration time interval in a first frequency band of a band group, a
second MB-OFDM symbol in a second 312.5 nS duration time interval
in a second frequency band of the band group, and a third MB-OFDM
symbol in a third 312.5 nS duration time interval in a third
frequency band of the band group. Other piconets may also transmit
concurrently using the same band group, discriminating themselves
by using different time-frequency codes and a distinguishing
preamble sequence. This method of piconets sharing a band group by
transmitting on each of the three 528 MHz wide frequencies of the
band group may be referred to as time frequency coding or time
frequency interleaving (TFI). Alternately, piconets may transmit
exclusively on one frequency band of the band group which may be
referred to as fixed frequency interleaving (FFI). Piconets
employing fixed frequency interleaving may distinguish themselves
from other piconets employing time frequency interleaving by using
a distinguishing preamble sequence. In practice four distinct
preamble sequences may be allocated for time frequency interleaving
identification purposes and three distinct preamble sequences may
be allocated for fixed frequency interleaving. In different
piconets different time-frequency codes may be used. In addition,
different piconets may use different preamble sequences.
[0008] The structure of a message packet according to the
Multi-band OFDM SIG physical layer specification comprises a
preamble field, a header field, and a payload field. The preamble
field may contain multiple instances of the distinct preamble
sequence. The preamble field may be subdivided into a packet and
frame detection sequence and a channel estimation sequence. The
channel estimation sequence is a known sequence that may be used by
a receiver to estimate the characteristics of the wireless
communication channel to effectively compensate for adverse channel
conditions. The preamble field, the header field, and the payload
field may each be subdivided into a plurality of OFDM symbols.
SUMMARY OF THE INVENTION
[0009] According to one embodiment, the present disclosure provides
a transmitter that includes a block encoder. The block encoder is
operable to encode a bit stream using a first block size for a
first portion of a message according to an orthogonal frequency
division multiplex protocol and a second block size for a second
portion of the message.
[0010] In another embodiment, the present disclosure provides a
method of communication. The method comprises block encoding a
first portion of a message according to a multi-band orthogonal
frequency division multiplex protocol into a plurality of blocks
having a first length and block encoding a second portion of the
message into one or more blocks having a second length. The second
length being less than the first length.
[0011] In other embodiment, a communication system is provided. The
communication system includes a first transceiver operable using a
first block size to block encode a first portion of a message
according to a multi-band orthogonal frequency division multiplex
protocol. The first transceiver is operable using a second block
size to block encode a second portion of the message. The first
transceiver is further operable to transmit the message. The
communication system also includes a second transceiver that is
operable to receive the message using a block decoder to decode the
first portion of the message based on the first block size. The
second transceiver is also operable to decode the second portion of
the message based on the second block size. The second transceiver
distinguishes the first portion of the message from the second
portion of the message based on a message length indication
provided in the first portion of the message.
[0012] These and other features and advantages will be more clearly
understood from the following detailed description taken in
conjunction with the accompanying drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a more complete understanding of the present disclosure
and the advantages thereof, reference is now made to the following
brief description, taken in connection with the accompanying
drawings and detailed description, wherein like reference numerals
represent like parts.
[0014] FIG. 1 depicts an exemplary wireless piconet for
implementing an embodiment of the disclosure.
[0015] FIG. 2 is a block diagram of a transmitter in communication
with a receiver according to an embodiment of the disclosure.
[0016] FIG. 3a is an illustration of a first block size according
to an embodiment of the disclosure.
[0017] FIG. 3b is an illustration of a second block size according
to an embodiment of the disclosure.
[0018] FIG. 4 is an illustration of two messages partitioned into a
plurality of blocks of a first block size and one or two final
blocks of a second block size according to an embodiment of the
disclosure.
[0019] FIG. 5 an exemplary general purpose computer system having a
radio transceiver card suitable for implementing the several
embodiments of the disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] It should be understood at the outset that although an
exemplary implementation of one embodiment of the present
disclosure is illustrated below, the present system may be
implemented using any number of techniques, whether currently known
or in existence. The present disclosure should in no way be limited
to the exemplary implementations, drawings, and techniques
illustrated below, including the exemplary design and
implementation illustrated and described herein.
[0021] Block coding and convolution coding are forward error
correction coding techniques that add redundancy to subject
information to promote reception of a transmitted signal bearing
the subject information. Block coding may provide an alternative to
convolution coding and may be preferred to convolution coding in
some communication environments. In other communication
environments, block coding may be combined with convolutional
coding, for example, Reed-Solomon codes may be concatenated with
convolutional codes as an outer code to provide additional coding
gain. The present disclosure teaches the use of a dual length block
code in an orthogonal frequency division multiplex system. In block
coding, a block of input information bits may be processed to
produce a block of output information bits. The number of output
bits is greater than the number of input information bits because
of the redundancy introduced during the block encoding process. The
ratio of input to output information bits may be referred to as the
coding rate. For example, when 1800 input information bits are
block encoded using 2400 output information bits, the coding rate
is {fraction (3/4)}.
[0022] In block coding, messages are comprised of a sequence of
complete blocks. Receivers may be required to receive a complete
block of output information bits, for example 2400 bits, before
decoding, which may produce a delay that is referred to as decoding
latency. When the number of input information bits does not fill
the last block, the last block may be filled by pad bits that carry
no meaningful information. Longer block sizes provide more usable
redundancy and are associated with greater coding gain or the
ability to receive the transmitted message at a receiver. At the
same time, longer block sizes lead to greater decoding latency.
Additionally, longer block sizes lead to the use of more pad bits
which constitute an overhead burden on the communications
throughput rate. On average, the number of pad bits employed per
message may be expected to be half of the block size. Using shorter
block sizes reduces overhead associated with pad bits and reduces
decoding latency. Shorter block sizes also have less coding gain.
The use of dual length block sizes may obtain the advantages of
both shorter and longer block sizes. The long block size may be
employed for the leading portion of the message and the short block
size may be employed at the end of the message. In some
embodiments, more than two block sizes may be employed.
[0023] Turning now to FIG. 1, a block diagram depicts a piconet 100
formed by a number of cooperating electronic devices. A first
transceiver 102 operates as the piconet controller for the piconet
100. A second transceiver 104, a third transceiver 106, and a
fourth transceiver 108 operate as member of the piconet 100. The
transceivers 102, 104, 106, and/or 108 may also be capable of
operating as the piconet controller of the piconet 100, but are not
depicted as carrying out that role. The first transceiver 102 may
broadcast beacon messages, which may be referred to simply as
beacons, to promote communication among the members of the piconet
100. The effective range of the beacon messages, and hence the
effective boundary of the piconet 100, is depicted by a dashed line
in FIG. 1. The first transceiver 102 may be connected to either a
public switched telephone network 110 or to a public switched data
network 112 whereby the members of the piconet 100, for example the
transceivers 102, 104, 106, and 108, may communicate with the
Internet or other network of interconnected communication devices.
The transceivers 102, 104, 106, and 108 may wirelessly communicate
according to the Multi-band orthogonal frequency division multiplex
(OFDM) Alliance (MBOA) Special Interest Group (SIG) Physical layer
specification, according to a WiMedia wireless personal area
network protocol, and/or according to an Ecma wireless personal
area network protocol. The wireless communications within the
piconet 100 are transmitted and received as a sequence of
orthogonal frequency division multiplex (OFDM) symbols. While the
description above focuses on a wireless multi-band OFDM system, one
skilled in the art will readily appreciate that the dual block size
block coding concept may be applied to other OFDM systems. Further,
the transceivers 102, 104, 106, and 108 may be operable for
implementing the present disclosure.
[0024] Turning now to FIG. 2, a wireless transmitter 200 is shown
in communication with a wireless receiver 202. Some conventional
elements of transmitters and receivers may be omitted from FIG. 2
but will be readily apparent to one skilled in the art. The
wireless transmitter 200 is suitable for transmitting OFDM symbols
formatted according to embodiments of the present disclosure, and
the wireless receiver 202 is suitable for receiving the OFDM
symbols formatted according to embodiments of the present
disclosure. A signal source 204 provides data to be transmitted to
a modulator 206. The modulator 206 may comprise a spreader or
scrambler component 201, a block encoder 203, an interleaver 205,
and a mapper 207. The scrambler component 201 processes the data,
which may be referred to as a bit stream, and provides input
information data to the block encoder 203. The block encoder 203
encodes the input information data into output information data in
a first block size for a first portion of the message and a second
block size for a second portion of the message. Reed-Solomon, low
density parity check, or other block coding mechanism or component
may be employed to block encode the information data. An
interleaver 205 may further process the bit stream. The output of
the interleaver 205 is provided to a mapper 207 that mounts the
output of the interleaver onto quadrature amplitude modulation
(QAM) constellations for each of the tones. The modulator 206
provides the tones to an inverse fast Fourier transformer component
208 which translates the frequency domain representation of the
data into a time domain representation of the same data.
[0025] The inverse fast Fourier transformer component 208 provides
the time domain representation of the signal to a digital-to-analog
converter 210 which converts the digital representation of the
signal to an analog form. The analog form of the signal is a 528
MHz wide baseband signal. The digital-to-analog converter 210
provides the 528 MHz wide baseband signal to an up converter 212
which frequency shifts the 528 MHz wide baseband signal to the
appropriate frequency band for transmission. The up converter 212
provides the up converted 528 MHz wide signal to an amplifier 214
which boosts the signal strength for wireless transmission. The
amplifier 214 feeds the up converted, amplified, 528 MHz wide
signal to a band-select filter 216, typically having a bandwidth of
1584 MHz, that attenuates any spurious frequency content of the up
converted signal which lies outside the desirable three bands of
the MB-OFDM signal. The band-select filter 216 feeds a transmitting
antenna 218 which wirelessly transmits the up converted, amplified,
band-select filtered 528 MHz wide signal.
[0026] The wireless signal is received by a receiving antenna 220.
The receiving antenna 220 feeds the signal to a receiving
band-select filter 222, typically having a bandwidth of 1584 MHz,
that selects all three bands of the MB-OFDM signal from the entire
bandwidth which the receiving antenna 220 is capable of receiving.
The receiving band-select filter 222 feeds the selected MB-OFDM
signal to a down converter 224 which frequency shifts the MB-OFDM
signal to a 528 MHz baseband signal. The down converter 224 feeds
the 528 MHz baseband signal to a base-band, low-pass filter 225,
typically having a 528 MHz bandwidth. The base-band, low-pass
filter 225 feeds the filtered 528 MHz baseband signal to an analog
to digital converter 226 which digitizes the filtered 528 MHz
baseband signal. The analog to digital converter 226 feeds the
digitized 528 MHz baseband signal to a fast Fourier transformer 228
which converts the digitized 528 MHz baseband signal from the time
domain to the frequency domain, decomposing the digitized 528 MHz
baseband signal into distinct frequency domain tones. The fast
Fourier transformer 228 feeds the frequency domain tones to a post
FFT processing block 227 that performs frequency domain
equalization to compensate for the multi-path channel, phase
tracking and correction and also the demapping. The post FFT
processing block 227 output feeds to a deinterleaver 229 that
reverses the processing performed in the transmitter 200 by the
interleaver 205. The deinterleaver 229 output feeds to a decoder
component 230 that extracts the data from the blocks. The decoder
component 230 output feeds to a descrambler component 231 which
reverses the processing performed in the transmitter 200 by the
scrambler component 201. The stream of data is then provided to a
medium access control (MAC) component 232 which interprets and uses
the stream of data.
[0027] The wireless transmitter 200 and wireless receiver 202
structures described above may be combined in some embodiments in a
single device referred to as a transceiver, for example the
transceivers 102, 104, 106, and 108 described above with reference
to FIG. 1. While the transmitting bandpass filter 216 and the
amplifier 214 are described as separate components, in some
embodiments these functions may be integrated in a single
component. Additionally, in some embodiments the up converted 528
MHz bandwidth signal may be bandpass filtered by the transmitting
bandpass filter 216 before it is amplified by the amplifier 214.
Other systems, components, and techniques may be implemented for
these purposes which will readily suggest themselves to one skilled
in the art and are all within the spirit and scope of the present
disclosure. For example, in a very high data rate digital
subscriber line system (VDSL), a hybrid may be provided to
interface the transmitter 200, the receiver 202, or a transceiver
to a digital subscriber line. In the VDSL example, the up converter
212, the first antenna 218, the second antenna 220, and the down
converter 224 may be unnecessary.
[0028] Turning now to FIG. 3a, a first block size is depicted. A
first block 300 is depicted as composed of twelve OFDM symbols 302.
The first block 300 is depicted as using 3/4 coding, but in other
embodiments other coding rates may be employed. Because in the
multi-band OFDM system, the time-frequency codes have a period of 6
OFDM symbols, each block is an integer multiple of six OFDM symbols
in length. At a 480 Mbps data rate, six OFDM symbols 302 may
contain 900 source information bits. Based on a 3/4 coding rate,
block sizes may be integer multiples of 1200 bits. The minimum
block sizes for other multi-band OFDM data rates is provided in
Table 1 below.
1TABLE 1 Data Rate Code Rate Source bits Minimum Block Size (3/4
rate) 480 Mbps 3/4 900 1200 400 Mbps 5/8 750 1200 320 Mbps 1/2 600
1200 200 Mbps 5/8 375 600 160 Mbps 1/2 300 600 106.7 Mbps 1/3 200
600 80 Mbps 1/2 150 300 53.3 Mpbs 1/3 100 300
[0029] Turning now to FIG. 3b, a second block size is depicted. A
second block 310 is depicted as composed of six OFDM symbols 312,
the period of the multi-band OFDM system time-frequency codes. With
reference to both FIGS. 3a and 3b, the first block size is 2400
bits and the second block size is 1200 bits. The first block size
may be employed to block code the initial portion of an OFDM
message and the second block size may be employed to block code the
end of the OFDM message. In another embodiment, more than two
different block sizes may be employed. For example, a third block
size, smaller than both the first and second block sizes, may be
employed to block code the end of the message.
[0030] Turning now to FIG. 4, a first block coded OFDM message 320
and a second block coded OFDM message 330 are depicted. The first
block coded OFDM message 320 comprises n first blocks 300 and a
single second block 310. In the first message 320, the remainder
bits of the first block coded OFDM message 320 that did not
completely fit into a first block size fit into a single second
block 310a. In the second message 330, the remainder bits do not
fit into the single second block 310 so two are employed, namely
second block 310a and second block 310b. While using two second
blocks 310, second block 310a and 310b, may not reduce pad bit
overhead versus using the single first block 300, the two second
blocks 310a and 310b may reduce the decode latency at the
completion of the second block coded OFDM message 320. Because a
receiver may be required to know where the OFDM message 320, 320
block size changes from the first block size to the second block
size, a header or leading portion of the OFDM messages 320, 330 may
include an indication of the number of source information bits. The
receiver may determine the number of blocks of the first block size
contained in the OFDM messages 320, 330 and hence what blocks to
decode according to the first block size and what blocks to decode
according to the second block size. If the length of the first
block 300 is selected to be twice the length of the second block
310, the following pairs of block sizes may be employed, where the
first number in the pair represents the number of bits in the first
block 300 and the second number in the pair represents the number
of bits in the second block 310: (2400 bits, 1200 bits), (1200
bits, 600 bits), and (600 bits, 300 bits). In other embodiments
other pairs of bit lengths may be associated with the first block
300 and the second block 310. Other possible pairs of block sizes
include (2400 bits, 600 bits), (2400 bits, 300 bits), and (1200
bits, 300 bits). Other pairs of block sizes are also contemplated
by the present disclosure.
[0031] While the first block 300 in these examples is twice the
length of the second block 310, the length of the first block 300
may have other lengths. The length of the first block 300 may be
other rational multiples of the length of the second block 310,
including integer multiples of the length of the second block 310.
In an embodiment, the first transceiver 102 and the second
transceiver 104 may conduct an initialization session in which the
length of the first block 300 and the second block 310 is
negotiated to obtain a mutually preferred length. For example,
different sizes of the second block 310 may be tested during a
training portion of initialization to obtain a specified maximum
packet error rate. Additionally, while the length of the second
block 310 in the example is selected as six symbols to conform to
the period of the multi-band OFDM time-frequency codes, in other
OFDM systems the length of the second block 310 may be from the
length of one OFDM symbol to the length of the number of OFDM
symbols that conforms to the period in those other OFDM
systems.
[0032] The transceivers 102, 104, 106, and 108 described above may
be implemented in various ways, including on a single integrated
circuit or on a plurality of integrated circuits coupled together
such as is well known to those skilled in the art. In one
embodiment the transceivers 102, 104, 106, and 108 are implemented
as a printed circuit card.
[0033] Turning now to FIG. 5, a system 360 illustrates an exemplary
piconet member device. A transceiver card 362 comprises an
application specific integrated circuit (ASIC) 364 or other form of
digital processor, the digital-to-analog converter 210, the
analog-to-digital converter 226, the amplifier 214, a receiver
amplifier 370, a switch 368, and a transmit/receive antenna 366.
The application specific integrated circuit 364 provides the
modulation/demodulation and fast Fourier transformer/inverse fast
Fourier transformer functions described above with respect to FIG.
3. The switch 368 selects whether the antenna receives a signal and
routes the signal to the receiver amplifier 370 or the antenna
transmits a signal routed from the amplifier 214. The application
specific integrated circuit 364 is coupled to a processor (which
may be referred to as a central processing unit or CPU) 382. The
CPU 382 provides a communication packet to the application specific
integrated circuit 364 and receives communication packets from the
application specific integrated circuit 364, for example data link
layer packets.
[0034] The processor 382 is in communication with memory devices
including secondary storage 384, read only memory (ROM) 386, random
access memory (RAM) 388, input/output (I/O) 390 devices, and
network connectivity devices 392. The processor may be implemented
as one or more CPU chips.
[0035] The secondary storage 384 is typically comprised of one or
more disk drives or tape drives and is used for non-volatile
storage of data and as an over-flow data storage device if RAM 388
is not large enough to hold all working data. Secondary storage 384
may be used to store programs which are loaded into RAM 388 when
such programs are selected for execution. The ROM 386 is used to
store instructions and perhaps data which are read during program
execution. ROM 386 is a non-volatile memory device which typically
has a small memory capacity relative to the larger memory capacity
of secondary storage. The RAM 388 is used to store volatile data
and perhaps to store instructions. Access to both ROM 386 and RAM
388 is typically faster than to secondary storage 384.
[0036] I/O 390 devices may include printers, video monitors, liquid
crystal displays (LCDs), touch screen displays, keyboards, keypads,
switches, dials, mice, track balls, voice recognizers, card
readers, paper tape readers, or other well-known input devices. The
network connectivity devices 392 may take the form of modems, modem
banks, ethernet cards, universal serial bus (USB) interface cards,
serial interfaces, token ring cards, fiber distributed data
interface (FDDI) cards, wireless local area network (WLAN) cards,
radio transceiver cards such as Global System for Mobile
Communications (GSM) radio transceiver cards, and other well-known
network devices. These network connectivity 392 devices may enable
the processor 382 to communicate with an Internet or one or more
intranets. With such a network connection, it is contemplated that
the processor 382 might receive information from the network, or
might output information to the network in the course of performing
the above-described method steps. Such information, which is often
represented as a sequence of instructions to be executed using
processor 382, may be received from and outputted to the network,
for example, in the form of a computer data signal embodied in a
carrier wave
[0037] Such information, which may include data or instructions to
be executed using processor 382 for example, may be received from
and outputted to the network, for example, in the form of a
computer data baseband signal or signal embodied in a carrier wave.
The baseband signal or signal embodied in the carrier wave
generated by the network connectivity 392 devices may propagate in
or on the surface of electrical conductors, in coaxial cables, in
waveguides, in optical media, for example optical fiber, or in the
air or free space. The information contained in the baseband signal
or signal embedded in the carrier wave may be ordered according to
different sequences, as may be desirable for either processing or
generating the information or transmitting or receiving the
information. The baseband signal or signal embedded in the carrier
wave, or other types of signals currently used or hereafter
developed, referred to herein as the transmission medium, may be
generated according to several methods well known to one skilled in
the art.
[0038] The processor 382 executes instructions, codes, computer
programs, scripts which it accesses from hard disk, floppy disk,
optical disk (these various disk based systems may all be
considered secondary storage 384), ROM 386, RAM 388, or the network
connectivity devices 392.
[0039] While several embodiments have been provided in the present
disclosure, it should be understood that the disclosed systems and
methods may be embodied in many other specific forms without
departing from the spirit or scope of the present disclosure. The
present examples are to be considered as illustrative and not
restrictive, and the intention is not to be limited to the details
given herein, but may be modified within the scope of the appended
claims along with their full scope of equivalents. For example, the
various elements or components may be combined or integrated in
another system or certain features may be omitted, or not
implemented.
[0040] Also, techniques, systems, subsystems and methods described
and illustrated in the various embodiments as discrete or separate
may be combined or integrated with other systems, modules,
techniques, or methods without departing from the scope of the
present disclosure. Other items shown or discussed as directly
coupled or communicating with each other may be coupled through
some interface or device, such that the items may no longer be
considered directly coupled to each other but may still be
indirectly coupled and in communication, whether electrically,
mechanically, or otherwise with one another. Other examples of
changes, substitutions, and alterations are ascertainable by one
skilled in the art and could be made without departing from the
spirit and scope disclosed herein.
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